Filament-current-reversing device



L. W. GILLIS FILAMENT CURRENT REVERSING DEVICE April 3, 1928.

' Filed July 19. 1927 INVENTOR. 0(5011/ W BY r 912M TTORNEYS.

Patented Apr. 3, 1928.

siren STATES LEON W. GILL IS, OF .ALDERWOOD MANOR, WASHINGTON.

FILAMEN'II-CURRENT-REVEBSING DEVICE.

Application filed July 19,

lhis invention relates to filaments of thermionic tubes and especially to means whereby the current flow through the filament may be reversed.

In vacuum tubes of the thermionic type wherein a filament is employed to cause electron emission and where direct current is used to bring the filament to a state of electronic emission, a one way load'is imposed upon the filament due to the filament resistance or drop. This drop causes one side of the filament to carry more current than the other side. This one way load is further increased by the unidirectional thermionic plate current being superposed upon the unidirectional filament current and there is accordingly a tendency to burn out one side of the filament.

A number of attempts have been made to reverse the current flow through the filament as such reversal from time to time would materially prolong the life of the filament, but such attempts have been more or less impractical, particularly in connection with ordinary radio receiving sets as it requires a change in the wiring connections and the interposition of one or more reversing switches or the like.

The object of the present invention is to generally improve and simplify the construction and operation of a filament current reversing device and especially to provide a current reversing device which is adapted to be interposed between thebayonet prongs and the tube base and the contacts of a standard tube socket, thereby permitting reversal of the filament current flow without the use of external switches and without disturbing the circuits or connections erzternal to the socket.

The invention is shown by way of illustration in the accompanying drawings in which:

Fig. I is a central vertical section of a standard form of thermionic. tube and a standard tube socket.

Fig. 2 is a similar section showing the interposition of the filament current reversing device.

Fig. 3 is a longitudinal vertical section of the filament current reversing device.

Fig. 4 is a cross-section taken on line IVIV, Fig. 3.

Fig. 5 is a cross-section taken on line V V Fig. 3. i

1927. Serial N0. 206,875,

Fig. 6 is a perspective view of the filament current reversing device.

Referring to the drawings in detail and particularly Figs. 1 and 2, A indicates a standard form of thermionic tube which in this instance is provided with a base portion 2 and bayonet prongs 3. The drawings also illustrate a standard form of tube socket of the open contact lock type generally indicated at B which is known in the art as a standard socket. with terminal connections such as shown at 3. and 4 and these are connected with resilient spring arm contact members 5 and 6 which in turn connect with the prongs 3 and thereby establish a circuit through the fila- The socket is provided ment, the grid, and the plate as indicated at 7, 8' and 9 respectively.

The filament current reversing device forming the subject matter of the present application is best illustrated in Figs. 3, 4: 5 ,and 6. By referring to Fig. 6 it will be noted that the filament current reversing device consists of an elongated block generally indicated at C which is constructed'of insulating material. The block is, provided with two-openings, one at each end as indicated at 10 and 11 which are provided for thed reception of the prongs indicated at 3 an 3*. bers generally indicated at 12 and 13. The contact members extend over each end of the member C, i. e., over the bottom face. They are then bent at right angles as indicated at 14 and are run on an angle across the side of the block as indicated at 15 where they are secured by means of screws 16.- They are then again'bent right angles to form loop or spring contacts as indicated at 17 which extend downwardly into the prong. receiving openings 10 and 11 In actual practice the tube A is inserted in the socket B the usual manner and when so inserted will assume the position shown in 1. It the filamentcurrent enters theterminal indicated which is the positive terminal of the socket, it will pass through the spring contact 6. the prong 3 an will. t r the l Qf he fi ame dicated at 7. The" current will then flow down the opposite leg of the filament shown at 7" and will then pass out through the prong 3 the spring contact 5, and the ter minal 4thus completing the circuit through the filament. It has already been The block carries two contact mem- 3o ment and out through the prong 3.

stated that vacuum tubes of the thermionic type wherein a filament is employed to cause electronic emission and where direct current is used to bring the filament to a state of 5 electronic emission; that a one way load is imposed upon the filament due to the filament resistance or drop; and further that I this one way load is'increased "by"'the1ther-' mionic plate current which is superposed upon the unidirectional filament current.

lVith these facts in mind it is more or less obvious that the leg of the filament indicated at 7 will be subjected to the greatest load and that this side of the filament will tend to burn out. Applicant has accordingly provided a simple means whereby the current flow may be reversed so that the load may be transferred.whenever desired from one side of the filament to the other.

.He accomplishes this by. inserting the current reversing device generally indicated at C (see Fig. 2). The current entering the positive terminal 3 will in that instance pass through. the spring contact 6 and as it engages the contact 12, the current will pass thus reversed and the load for the time being will be imposed on the leg 1 thereof. The current may again be reversed by removing the device C When the circuit through the filament will. be such as shown in Fi g. 1. By so reversing the current from time to time thelife of the-filan'ient and the tube as a whole is materially prolonged and maximum electronic emission obtained. It Will further be noted that the reversing of the current is accomplished without disturbing anexternal wiring or connections, and

without employing, exterior switches or the like.

While certain features of the present in vention are more or less specifically described, I wish it understood that various changes may be resorted to within the scope of the appended claims; similarly, that various-materials and finishes of the several parts employed may be such as the manufacturer may decide or varying conditions or uses may demand.

Having thus described my invention, what wvith the prongs, asocket to receive the base and the prongs, contact members in the base engageable with the prongs to close an electric circuit through" the filament in one di-} rection, and means insertable between the prongs and the contacts of the socket to reverse the current fiow through the filament.

2. In a thermionic tube having a base provided With prongs and a filament connected with the prongs, a socket to receive the base and the prongs, contact members in the base engageable with the prongs to close an electric circuit through the filament in one direction, means insertable between the prongs and the contacts of the socket to reverse the current flow through the filament, said means comprising a block of insulating material having a pair of openings formed therein adapted to receive the prongs of the base, and a'pair of contact members carried by said block, said cont-act members having two terminals, one end of each terminal being engageable with one 01": the prongs of the tube and the opposite terminal of each contact being engageable with the spring contacts oi the socket. V

3. In a thermionic tube having a base provided with prongs and a filament connected with the prongs, a socket to receive the base'and the prongs, contact members in the base engageable with the prongs to close an electric circuit through the filament in one direction, means insertable between the prongs and the contacts of the socket to reverse the current flow through the filament, said means comprisingan elongated block of insulating material having two openings formed therein to receive the prongs of the tube base, and a pair of contact members carried by said insulating LEON w. einn sf 

